The present invention relates to a method and an apparatus for treating limescale deposits within water heaters in beverage dispensing machines.
Water heaters are known to be subject to limescale build-up on the surfaces which contact the water. In fact heating the water leads to the ionization of the dissolved salts, and these tend to deposit in a layer on the surface of the water heater. The limescale build-up causes formation of hard deposits which are difficult to remove and detrimental to the operation of the heater and the associated ducts. Such deposits reduce the efficiency of the thermal exchange between the hot surfaces of the heater and the water, thereby causing waste of energy. Moreover an excessive build-up of limescale may cause ducts to be obstructed.
Different apparatuses have been provided for reducing, by way of vibrations, the limescale build-up within water heaters, such as boilers, flash-heaters, etc.
EP-A-1378194, in the name of “Fianara International B.V.”, discloses an apparatus for preventing the limescale deposits within the water heater of a beverage dispensing machine. The apparatus is provided with an ultrasound transmitter and an ultrasound receiver, such as piezo-electric transducers, directly or indirectly coupled to the water heater. The ultrasound transmitter is powered during all the operation time of the beverage dispensing machine to generate oscillations which are transmitted to the heater body and then picked up by the receiver. An amplifier amplifies the oscillations and, without altering the phase, feeds back the oscillations to the transmitter, through the heater body. In this way a feedback loop is provided which makes the water heater to oscillate at its natural frequency, thereby avoiding the limescale build-up over the heater surfaces. The apparatus provides low power of piezo-electric transducers, included in the range from 100 mW to 250 mW, for long time.
The apparatus according to EP-A-1378194 requires an amplifier to be provided with an ultrasound receiver and the related circuitry, this leading to a complicated assembly and high production and maintenance costs. Setting up the circuitry can be complicated. The amplifier and the circuitry need to be cooled, especially if located next to the water heater, this requiring a particular attention during installation of the apparatus.
Moreover if the piezo-electric transducers are made of a ceramic material, they must be thermally isolated from the water heater. In fact, when the temperature of the transducers exceeds the Curie temperature of the ceramic material, the transducers cease to operate. Thus an insulating material must be provided between each transducer and the water heater. Such insulating material should promote sound transmission in order to allow propagation of the oscillations.
GB-A-2227254, in the name of “Instants Limited”, refers to a method and the related apparatus for removing, or preventing, the formation of limescale deposits within a water heater. Water is oscillated at high frequencies by inducing ultrasonic vibrations, for instance by way of a piezo-electric device, in the range of 20 kHz to 100 kHz. Vibrations, which are transmitted to the water heater, are generated continuously to avoid a limescale build-up or to remove the deposits. Known methods and apparatuses for removing or preventing limescale build-up within water heaters have several drawbacks.
Causing the water heater to vibrate at its natural frequency may easily occur in troublesome noise generation. Moreover the water heater must be expressly designed to sustain the mechanical stresses which are maximized, in that the oscillations are at the heater natural frequency. Heaters normally utilized within beverage dispensing machines have a simple design and are unexpensive. Weldings, fittings, couplings, etc., between heater parts may fail under uninterrupted vibrations. A design of the water heater which takes into account such risks easily leads to an increase of production costs.
Causing the water heater to continuously vibrate, for long time, at high frequencies may also result in mechanical failures. Moreover such a solution is power consuming.